Internal high pressure forming device and method and corresponding tool system

ABSTRACT

The invention relates to a hydroforming device and a hydroforming process and also to a hydroforming die arrangement. To make it possible to produce even complex three-dimensional sheet-metal shapes while ensuring that the deformation process takes place without disruption, the device comprises a die ( 5 ) which is divided into two die halves ( 5   a   , 5   b ) along a die parting plane, the two die halves ( 5   a   , 5   b ) forming at least one forming chamber ( 6 ) which can be acted on by a hydrostatic internal pressure (Pi) for forming purposes at a workpiece ( 7 ) which is to be deformed, a die carrier ( 2 ), which for each die half ( 5   a   , 5   b ) has at least one die carrier component ( 3, 4 ) assigned to this die half ( 5   a   , 5   b ), each pair made up of die carrier component ( 3, 4 ) and die half ( 5   a   , 5   b ) being assigned at least one fluid chamber ( 8 ) which is formed from a piston component and a piston-receiving component, and means being provided for producing a hydrostatic fluid chamber pressure (Pa) which is at least equal to the hydrostatic internal pressure (Pi) and, compensating for the hydrostatic internal pressure (Pi), exerts a die-closing force on the two die halves ( 5   a   , 5   b ).

[0001] The invention relates to a hydroforming device and a hydroforming process and to a hydroforming die arrangement.

[0002] Hydroforming is used to deform workpieces by application of hydrostatic pressure and is employed, for example, in the automotive industry. In this case, the workpiece which is to be processed is surrounded by a shaping, generally split die, which has a fluid feed line for application of the hydrostatic pressure which is required to deform the workpiece. The workpieces which are to be deformed may, for example, be tubes or plates, the forming chamber which is located in the interior of the die and is in communication with the fluid feed line being designed to match the desired shape of the deformed workpiece.

[0003] Since, on account of the hydrostatic pressure introduced, the die halves which form the die endeavour to drift apart, a closure-holding device, i.e. a die carrier for clamping the die in place, and the closure-holding force which is exerted on the die by the closure-holding components or die carrier components has to be greater than or equal to the force which results from the hydrostatic internal pressure which has been introduced into the forming chamber. Depending on the level of the internal pressure which is required for deformation of the workpiece, the closure-holding forces required may be so great that elastic deformations occur in the components of the die carrier, and these are in turn transferred to the die halves. Consequently, the precision positive lock of the die which is required for hydroforming is no longer present, with the result that the internal pressure can locally escape at the leaks which are formed, and the deformation process is interrupted. This problem is particularly serious if relatively complex deformation operations are to be performed, in order, for example, to deform metal sheets, e.g. for automotive bodywork parts, in a plurality of planes, since the parting planes between the die halves are then three-dimensionally curved, and the demands imposed on the corresponding sealing surfaces which seal off the forming chamber are correspondingly high. Consequently, deformation of complex, three-dimensional sheet-metal geometries, for example for automotive bodywork parts, is in practice possible with the known hydroforming processes and devices.

[0004] A hydroforming device and hydroforming process in which the closure-holding force required to compensate for the internal pressure is produced by means of a cylinder assembly arranged beneath a press platen are known. Moreover, by suitably connecting and controlling the cylinders, it is possible to accurately determine the closure-holding forces according to the demands imposed on the die. To limit the influence of elastic deformations in the die carrier components, it is provided with structural reinforcements in the form of increases in the wall thickness. On account of the deployment of large quantities of material required for this purpose, however, the overall size, complexity and weight of the die carrier are increased considerably, with the result that on the one hand devices of this type are difficult and expensive to procure, install and operate and, on the other hand, the abovementioned high demands imposed on the sealing surfaces for sealing off the deformation chamber when deforming complex three-dimensional sheet-metal geometries are not satisfied.

[0005] DE 197 16 663 C1 has disclosed a device for the hydrostatic deformation of cold-formable flat metallic material, in which the sheet-metal body which is to be shaped is held between two female die plates, one of which has an engraved structure corresponding to the desired shape, a press ram which is mounted such that it can move in the vertical direction acting on the upper female die plate. At least one of the two female die plates is of flexible design, and a layer which is clamped in place on all sides and has a hydraulically passive action is arranged between the flexible female die plate and the press ram.

[0006] Although the fact that the female die plate nestles against the surface of the flat material which is to be deformed within a certain pressure range alleviates the effects of deformation of the female die plate on the seal during the deformation process, this compensation is only sufficiently effective within a restricted pressure range, meaning that when high die-closing forces are required, additional structural reinforcements are also required in order to maintain the required positive lock between the die halves.

[0007] DE 198 34 471 A1 has disclosed a device for carrying out a hydroforming operation which has a pressure vessel which is arranged in a frame and comprises upper and lower vessel parts, which each bear mould parts therein. Between the mould parts there is a mould cavity in which a workpiece which is to be processed by means of hydroforming is arranged. Furthermore, an expandable bellows, into which a pressurized fluid is introduced while the mould cavity is being acted on by likewise a pressurized fluid, in order to prevent the mould parts from drifting apart, is arranged between one or both mould parts and the associated upper and lower vessel parts.

[0008] However, this device firstly has the drawback that the flexible materials which are required to form the flexible bellows, when high pressures are introduced, has the property of being able to penetrate into any gaps, even extremely small ones, which form in the device. Moreover, to allow the vessel part which is in each case located above or below the bellows to move in the vertical direction, it is for design reasons necessary to take account of a gap dimension between the vessel part and the corresponding mould part, with the result that the flexible, inflatable bellows can work its way into the gap during the hydroforming operation and will sooner or later be destroyed. Furthermore, in this device too, elastic deformations to the corresponding vessel part are transferred via the flexible bellows to the adjoining mould part, so that given correspondingly high pressures the required precision form fit between the die halves is no longer ensured. This is true in particular if, as described above, complex sheet-metal geometries are being shaped, since at the three-dimensionally curved sealing surfaces which are then required, the flexible bellows is insufficient to compensate for the said elastic deformations.

[0009] Therefore, it is an object of the invention to provide a hydroforming device and a hydroforming process with which even complex, three-dimensional sheet-metal geometries can be achieved while it is ensured that a deformation process takes place without disruption.

[0010] This object is achieved in accordance with the features given in the independent claims.

[0011] To this end, a hydroforming device comprises

[0012] at least one die which is divided into two die halves along a die parting plane, the two die halves forming at least one forming chamber which can be acted on by a hydrostatic internal pressure for forming purposes at a workpiece which is to be deformed,

[0013] a die carrier, which for each die half has at least one die carrier component assigned to this die half,

[0014] each pair made up of die carrier component and die half being assigned at least one fluid chamber which is formed from a piston component and a piston-receiving component, and

[0015] means being provided for producing a hydrostatic fluid chamber pressure, which is at least equal to the hydrostatic internal pressure, in each of the fluid chambers, which fluid chamber pressure, compensating for the hydrostatic internal pressure, exerts a die-closing force on the two die halves.

[0016] On account of the fluid chambers according to the invention, which can be acted on by a hydrostatic fluid chamber pressure which compensates for the hydrostatic internal pressure in the forming chamber, it is possible for the closure-bonding force which is required for the purpose of maintaining a positive lock between the die halves during the deformation process to the die halves without elastic deformations of the die carrier components being transferred to the die halves. This is because such deformations in each case cancel one another out on the sides of the corresponding die carrier components which face the die halves and therefor only occur at those side faces of the die carrier which are remote from the die halves, where they are, for example, dissipated into a frame of the hydroforming device. In this way, the required precision positive lock for ensuring that a deformation process proceeds without disruption is guaranteed even when forming complex workpieces, for example metal sheets with three-dimensionally curved surfaces.

[0017] Since in this way the elastic deformations of the die carrier components in the direction of the corresponding die halves are compensated for in a self-regulating manner, the remaining elastic deformations of the die carrier components have no effect on the sealing during the deformation process, meaning that in particular there is no need for any additional structural reinforcements or increases to the wall thickness, but rather devices can be produced in lightweight structure.

[0018] The device according to the invention or the corresponding process also has the advantage that it is also possible for fluid chambers of a plurality of die carrier components to be connected next to one another in an assembly, so that it is possible to produce devices with considerable overall sizes of a length of many metres and with high closure-holding forces, which is important in particular when deforming very large plates, e.g. for metal cladding panels in the construction industry, but also for aeronautics, marine engineering applications and rail-borne transport.

[0019] According to an advantageous configuration, at least one pair comprising piston component and associated piston-receiving component is formed by two die carrier fixtures of the die carrier component in question. However, it is also possible for at least one pair comprising piston component and associated piston-receiving component to be formed by a die carrier component and the associated die half.

[0020] According to a further advantageous configuration, in the case of at least one die carrier component the associated die carrier fixture is provided with piston-like projections in order to form the piston component, and the other die carrier fixture is provided with corresponding cavities. In this case, each pair comprising cavity and piston-like projection can in each case enclose a fluid chamber, or alternatively it is possible to form a single common fluid chamber by using the entire area which remains between the cavities and the piston-like projections as a hydraulically acting surface.

[0021] According to a further advantageous configuration, there are means for guiding the die carrier components in the hydroforming device, e.g. along a frame in the hydroforming device.

[0022] According to a further advantageous configuration, each die half is assigned at least two adjacent fluid chambers, with in each case a multiplicity of fluid chambers arranged in matrix form preferably being provided on opposite die sides.

[0023] Consequently, the device according to the invention has considerable flexibility with regard to the positioning of the die halves in the die carrier, since the fluid chambers can be acted on by the hydrostatic external pressure either jointly or alternatively only partially, e.g. in a manner which is synchronized to one another at the top and bottom. In this way, there is no need for either central positioning of the die or a certain minimum size of the die carrier components in order to achieve a uniform closure-holding distribution, with the result that it becomes considerably easier to mount the device according to the invention compared with known devices.

[0024] According to a further advantageous configuration, fluid chambers which are respectively assigned to two different die halves are arranged opposite one another, so that it is ensured that, given an identical application of pressure to the fluid chambers lying opposite one another, an equal fluid chamber pressure is generated on both sides.

[0025] According to a further advantageous configuration, each pair comprising piston component and associated piston-receiving component in each case forms a sealing unit which closes off each fluid chamber in a pressure-tight manner. However, it is also possible for only the outer edge region of the corresponding die carrier component to be sealed, so that the entire space which remains inside the seal between the die carrier fixtures of the die carrier component can be used as a hydraulically acting surface.

[0026] Perpendicular to the piston axis, the fluid chambers may in each case have a cross section which is round, oval or of any other desired form, e.g. triangular or square.

[0027] According to a further advantageous configuration, the means for producing the hydrostatic fluid chamber pressure are configured in such a way that the fluid chambers, partially and/or jointly, can be acted on by an identical or different fluid chamber pressure. In this way, it is possible to achieve a maximum degree of flexibility with regard to the positioning of the die between the die carrier components and therefore an easy mounting/handling operation.

[0028] According to a further advantageous configuration, the means for producing the hydrostatic fluid chamber pressure are configured in such a way that the fluid chamber pressure which is produced in the fluid chambers located opposite one another is in each case identical. However, even more advantageously the means for producing the fluid chamber pressure are configured in such a way that the forces exerted on the two die halves by the fluid chamber pressure are oppositely directed and are of equal magnitude.

[0029] According to a further advantageous configuration, there is a control circuit for controlling the hydrostatic fluid chamber pressure as a function of the force exerted on the corresponding die half. In this way, it is possible to compensate for deviations in the size of the active surfaces of the die carrier components, for example resulting from manufacturing-related tolerances, so that a defined force is exerted on the die half in question irrespective of the size of the corresponding active surface.

[0030] According to a further advantageous configuration, between the two die halves of the die, in the die parting plane, there is a forming element, which together with each of the die halves, in each case forms a forming chamber which can be acted on by a hydrostatic internal pressure for shaping purposes at in each case one workpiece which is to be deformed. The forming element is preferably of mirror-symmetrical construction with respect to the die parting plane.

[0031] In this way, it becomes possible, when in each case one workpiece which is to be deformed is positioned in each of the two forming chambers, to form two corresponding components in a single production step by hydrostatic application of an identical hydrostatic internal pressure to the two forming chambers, since during the application of hydraulic force the forming element exerts a shaping action on the workpiece located in each forming chamber on both sides, i.e. in each of the two forming chambers.

[0032] This firstly creates a particularly efficient production process. Secondly, however, it is in this way possible to produce a pair of accurately matching components in a simple way, which is very important for example for the production of sandwich-like structures of thin metal sheets which are to be formed with in each case complex surface geometries.

[0033] According to a preferred embodiment, the forming element, between the die halves, is secured to a frame which bears the die carrier. This configuration is particularly advantageous since to fit workpieces which are to be treated into the hydroforming device and to remove them after the deformation operation, the two die halves or the associated die carrier components can simply be slid apart in the vertical direction while the forming element remains in its defined position.

[0034] However, the forming element may also be surrounded in a pressure-tight manner by the die halves, and in particular may also be mounted in a floating position between the two die halves. The “floating” mounting is in this case to be understood as referring to the vertical direction facing the respective die halves, i.e. the forming element which is surrounded by the die halves or enclosed by them in a pressure-tight manner can be displaced in this vertical direction, whereas in the horizontal direction it is surrounded by the die halves and consequently retains a defined position.

[0035] According to a further preferred embodiment, a plurality of dies with a forming element provided in the die parting plane between the respective die halves are arranged adjacent to one another in a direction perpendicular to the die parting plane.

[0036] According to a further preferred embodiment, in the die parting plane of at least one of the dies, there is a forming element provided between the respective die halves, which forming element, together with each of the associated die halves, in each case forms a forming chamber which can be acted on by a hydrostatic internal pressure for shaping purposes at in each case one workpiece which is to be deformed.

[0037] According to a further advantageous configuration, the die carrier is integrated in a clamping table (press platen) for clamping the die halves in place. This is advantageous in particular if an assembly is formed between a plurality of press platens in order to achieve an increased overall size.

[0038] According to a further aspect of the invention, a plurality of dies, which are in each case divided into two die halves along a die parting plane, are arranged in a stacked arrangement in a direction perpendicular to the die parting planes,

[0039] in which arrangement, during mounting of the die arrangement between in each case two adjacent die halves together with a workpiece which is to be deformed, a pressure chamber, which can be acted on by a hydrostatic internal pressure for shaping purposes at the workpiece, is formed by the workpiece and one die half, and a deformation chamber is formed by the workpiece and the other die half; and

[0040] the deformation chamber being in fluid communication, via the respectively adjacent die half, with the surroundings of the die arrangement, so that when pressure is applied to the pressure chamber, pressure is prevented from building up in the deformation chamber.

[0041] A hydroforming die arrangement of this type has the advantage over a conventional hydroforming die that the number of deformed workpieces ejected per operation is increased, since at each deformation cycle in the hydroforming die arrangement, a plurality of workpieces can be formed simultaneously. On account of the fluid connection between each deformation chamber and the surroundings of the die arrangement via the respectively adjoining die half, it is in this case ensured that the deformation can take place particularly easily, since a build-up of pressure in the deformation chambers is effectively prevented during each deformation process, i.e. during the application of hydrostatic internal pressure to the pressure chambers.

[0042] In this way, it is possible to produce particularly large numbers of workpieces per operation, which significantly increases the economic viability of the arrangement. Therefore, the drawback of relatively long cycle times which is usually cited in connection with hydroforming in comparison with conventional processes, such as deep-drawing or stamping, is considerably alleviated.

[0043] A hydroforming die arrangement of this type is particularly suitable for use in the hydroforming device described above, but can also be used in a conventional hydroforming device in which the closure-holding force which is required to compensate for the internal pressure is generated, for example, by means of cylinder assemblies arranged beneath the press platen. The die arrangement is suitable for use in a conventional hydroforming device in particular if workpieces with a substantially planar geometry are to be produced instead of complex three-dimensional sheet-metal geometries.

[0044] According to a further preferred embodiment, the die half which adjoins the corresponding deformation chamber has outlet openings extending from the surroundings of the die to the corresponding deformation chamber, in order to ensure the fluid connection between the corresponding deformation chamber and the surroundings of the die arrangement.

[0045] The outlet openings preferably comprise at least one outlet passage extending parallel to the die parting plane and a plurality of outlet passages arranged perpendicular thereto.

[0046] According to a further preferred embodiment, the die half which adjoins the corresponding deformation chamber is divided along the die parting plane at least into two separate components, which each have outlet openings extending perpendicular to the die parting plane towards the corresponding deformation chamber. This type of design of the die half is particularly favourable in terms of manufacturing technology, since, for example, the outlet passages which are to be formed in each of the die halves perpendicular to the die parting plane have a reduced length when the die half is of two-piece design compared to a single-piece design.

[0047] According to a further preferred embodiment, the stacked arrangement is such that in each case one die half which in each case forms a deformation chamber with the adjacent workpieces and one die half which in each case forms a pressure chamber with the adjacent workpieces are arranged adjacently, in an alternating sequence, perpendicular to the die parting plane. A stacked arrangement of dies in the hydroforming device of this type also makes it possible to increase the number of workpieces which can be produced per operation and therefore the economic viability of the installation to a considerable extent.

[0048] According to a further preferred embodiment, at least one of the die halves which in each case forms a pressure chamber with the adjacent workpieces has a fluid passage, which branches off towards the two workpieces, for applying the hydrostatic internal pressure to the pressure chambers. This ensures that the respective pressure chambers which are in communication with the branched fluid passage can be acted on by an identical hydrostatic pressure in a particularly simple way.

[0049] According to a further preferred embodiment, at least one of the die halves which in each case forms a pressure chamber with the adjacent workpieces has two fluid passages which branch off in opposite directions for independent application of the hydrostatic internal pressure to the corresponding pressure chambers. This ensures that the corresponding pressure chambers are in communication with separate fluid passages and can therefore be acted on by different hydrostatic pressures.

[0050] According to a further preferred embodiment, the stacked arrangement is such that in each case one pressure chamber and one deformation chamber are formed in an alternating sequence perpendicular to the die parting plane.

[0051] In the hydroforming process according to the invention, in at least one die, which is divided into two die halves along a die parting plane, at least one forming chamber, which is formed by the die halves, is acted on by a hydrostatic internal pressure for shaping purposes at a workpiece which is to be deformed, and a hydrostatic fluid chamber pressure, which is in each case at least equal to the internal pressure and, compensating for the hydrostatic internal pressure, exerts a die-closing force on the two die halves, is produced in fluid chambers which are formed from a piston component and a piston-receiving component and are each assigned to one of the die halves.

[0052] According to a further advantageous configuration, in each case a plurality of adjacent fluid chambers on opposite sides of the die are partially and/or jointly acted on by an identical or different fluid chamber pressure.

[0053] According to a further advantageous configuration, the hydrostatic fluid chamber pressure is controlled as a function of the force which is exerted on the corresponding die half by the fluid chamber.

[0054] According to a further preferred embodiment, in the die, two forming chambers, which are arranged opposite one another and are each formed by in each case one of the die halves with a forming element arranged in the die parting plane between the two die halves of the die, are simultaneously acted on by a hydrostatic internal pressure.

[0055] The forming element is preferably arranged mirror-symmetrically with respect to the die parting plane, and the two forming chambers, in order to form two identical components from workpieces which are in each case to be deformed, are simultaneously acted on by an identical hydrostatic internal pressure.

[0056] According to a further preferred embodiment, in a plurality of dies which are arranged adjacent to one another perpendicular to the respective die parting plane and have forming elements provided in the respective die parting plane between the respective die halves, a plurality of forming chambers, which are in each case formed by in each case one of the die halves and one of the forming elements, are simultaneously acted on by a hydrostatic internal pressure.

[0057] According to a further aspect of the invention, in a hydroforming process in which, in a hydroforming die arrangement in which a plurality of dies, which are in each case divided into two die halves along a die parting plane, are arranged in a stacked arrangement in a direction perpendicular to the die parting planes,

[0058] the die arrangement is equipped, between in each case two adjacent die halves, with a workpiece which is to be deformed, so that a pressure chamber is formed by the workpiece and one die half and a deformation chamber is formed by the workpiece and other die half;

[0059] each of the pressure chambers is acted on by a hydrostatic internal pressure for shaping purposes at the corresponding workpiece; and

[0060] when pressure is applied to the pressure chamber, a build-up of pressure in the deformation chamber is prevented by means of at least one fluid connection between the respectively adjacent die half and the surroundings of the die arrangement.

[0061] Further configurations of the invention are to be found in the following description and in the subclaims.

[0062] The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the appended figures, in which:

[0063]FIG. 1 shows a diagrammatic side view, partially in section, of a hydroforming device according to the invention;

[0064]FIG. 2 shows a cross-sectional view on section lines “A-A” through the lower die carrier component of the hydroforming device shown in FIG. 1;

[0065]FIGS. 3a and 3 b show perspective views of the lower die carrier component of the hydroforming device shown in FIG. 1; and

[0066]FIGS. 4a-d show a plan view of various preferred embodiments of a die carrier fixture which is used in the hydroforming device shown in FIG. 1;

[0067]FIG. 5 shows a cross-sectional view through an alternative embodiment of a die carrier component for the hydroforming device according to the invention;

[0068]FIGS. 6 and 7 show diagrammatic illustrations explaining the principle on which the hydroforming device according to the invention is based without (FIG. 6) and with (FIG. 7) the application of hydrostatic pressure;

[0069]FIG. 8 diagrammatically depicts an excerpt of a hydroforming device in which a die in accordance with a further preferred embodiment is provided;

[0070]FIG. 9 shows a diagrammatic cross-sectional view through an assembly of two die carriers for a hydroforming device;

[0071]FIGS. 10a-d show various embodiments of hydroforming die arrangements in accordance with a further aspect of the invention; and

[0072]FIGS. 11a-c show various embodiments of die components for use in one of the hydroforming die arrangements shown in FIG. 10.

[0073] In accordance with FIG. 1, a hydroforming device 1 according to the invention comprises, in a preferred embodiment, a die carrier 2, which comprises an upper die carrier component 3 and a lower die carrier component 4. The die carrier 2 is held by a frame (not shown here), which, in accordance with FIG. 9, may in a known way be composed, for example, of horizontal connecting bars secured to vertically arranged lamellae. The die carrier components 3, 4 of the die carrier 2 are then guided in such a manner that they can move in the vertical direction and be locked in place on the vertical steel lamellae of the frame. In particular, the lower die carrier component may be integrated in a clamping table (press platen) of the hydroforming device 1.

[0074] The die carrier components 3, 4 each have an upper die carrier fixture 3 a and 4 a, respectively, and a lower die carrier fixture 3 b and 4 b, respectively. A die 5, which comprises an upper die half 5 a and a lower die half 5 b, is mounted between the die halves 3, 4. On its side which faces the upper die half 5 a, the lower die half 5 b has an approximately centrally arranged recess, so that when the die halves 5 a, 5 b bear areally against one another, a forming chamber 6 is formed, in which a workpiece 7 which is to be deformed is arranged. The forming chamber 6 is designed to match the desired shape of the deformed workpiece and may also be provided at any other desired location between the die halves 5 a, 5 b.

[0075] Furthermore, the die half 5 a has a fluid passage which is in communication with the forming chamber 6 and inside the die half 5 a leads laterally outwards (in accordance with the illustration in FIG. 6). To process the workpiece 7, a preferably incompressible fluid (e.g. water or oil) is fed to the forming chamber 6 via the fluid passage by means of a hydraulic pump, with the result that an internal high pressure Pi which is required for deformation of the workpiece 7 is produced in the forming chamber 6.

[0076] In the process, the hydrostatic internal pressure Pi produced in the interior of the forming chamber 6 produces an outwardly directed force Fi=Pi×A, where A denotes the projected surface area of the surrounding wall of the forming chamber 6 onto the parting plane of the two die halves 5 a, 5 b, acting on the two die halves 5 a, 5 b. To maintain a sealed, areal contact between the die halves 5 a, 5 b, therefore, it is necessary for a force Fa to act on the die halves 5 a, 5 b from the outside, and the condition Fa≧Fi has to be satisfied throughout the entire deformation process.

[0077] In the hydroforming device 1 according to the invention, fluid chambers 8 which are in each case provided in the upper and lower die carrier components 3, 4 and the arrangement of which is illustrated in more detail in the lower die carrier component 4 in FIGS. 2 and 3a, b (the upper and lower die carrier components 3, 4 may be of identical construction) are used to produce the force Fa which acts on the die halves 5 a, 5 b from the outside.

[0078] In accordance with FIG. 2 and FIGS. 3a, b, the upper die carrier component 3 and the lower die carrier component 4 each comprise a large number of fluid chambers 8 which are arranged in matrix form and in the preferred embodiment illustrated are arranged in such a way that in each case a fluid chamber 8 in the lower die half 4 and a fluid chamber 8 in the upper die half 3 lie opposite one another on a force line. In the exemplary embodiment illustrated, each die carrier component 3, 4 in each case comprises a 3×6 matrix of fluid chambers 8, although it is possible to provide any desired number of fluid chambers 8. In this case, however, the upper and lower die carrier components 3, 4 preferably each comprises at least two adjacent fluid chambers 8, so that by partial actuation of these chambers it is possible to increase the flexibility with regard to the positioning of the die during mounting of the hydroforming device.

[0079] In accordance with FIG. 1 (bottom right hand-part) as well as FIGS. 2 and 3, each of the fluid chambers 8 is formed by the die carrier fixtures 4 a, 4 b of the lower die half 4 having positively and negatively shaped contours which correspond to one another and substantially form a positive lock with one another. For this purpose, in accordance with FIGS. 3a, b, the upper die carrier fixture 4 a has a piston-receiving component, and the lower die carrier fixture 4 b has a corresponding piston component.

[0080] The upper die carrier fixture 4 a comprises, as a piston-receiving component, a matrix-like arrangement (in the exemplary embodiment illustrated a 3×6 matrix) comprising substantially cylindrical cavities 13 which are open towards the side facing the lower die carrier fixture 4 b, whereas the lower die carrier fixture 4 b comprises, as piston component, a corresponding matrix-like arrangement (in the exemplary embodiment illustrated likewise a 3×6 matrix) of piston-like projections 14 which correspond to the cavities 13. The piston-like projections 14 of the lower die carrier fixture 4 b are arranged at positions which correspond to the cavities 13 of the upper die carrier fixture 4 a, so that the lower and upper die carrier components 4 a, 4 b engage together in a substantially positively locking manner. The position of the cavities 13 and of the piston-like projections 14 may also be swapped over compared to the embodiment illustrated in FIGS. 3a, 3 b, such that the cavities 13 are provided in the lower die carrier fixture 4 b of the lower die carrier component 4 (or in the upper die carrier fixture 3 a of the upper die carrier component 3).

[0081] Furthermore, the lower die carrier fixture 4 b, to form fluid passages 9, in accordance with FIG. 3b preferably has cylindrical bores, which in the exemplary embodiment illustrated are in each case arranged centrally in the corresponding piston-like projections 14 and extend from that side of the corresponding piston-like projection 14 which faces the corresponding cavity 13 to that side of the lower die carrier fixture 4 b which is remote from the cavity 13. However, the bores used to form the fluid passages 9 may also be formed in a corresponding way in the upper die carrier fixture 4 a, i.e. leading from the outside to the cavities 13.

[0082] To seal off the fluid chamber 8, each cavity 13 comprises a groove 11 which, in the engaged position of the lower and upper die carrier fixtures 4 a, 4 b, runs concentrically around the corresponding piston-like projection 14 and in which a sealing ring 12 is accommodated to form a seal 10, so that the piston component formed by one die carrier fixture 4 b and the piston-receiving component formed by the other die carrier fixture 4 a form a sealing unit which seals off each fluid chamber 8 in a pressure-tight manner with respect to the outside.

[0083] As an alternative to the preferred embodiment illustrated, it is possible for at least one pair comprising piston component and associated piston-receiving component for forming the fluid chambers 8 also to be formed by a die carrier component and the associated die half. In this case, the die carrier component in question can be of single-piece design and have piston-like projections 14 corresponding to those shown in FIGS. 3a, 3 b on that side face of the die carrier component in question which faces the respectively associated die half 5 a, 5 b, the corresponding cavities 13 then being provided in that side face of the corresponding die half 5 a or 5 b which faces this die carrier component. This type of design of the fluid chambers 8 can be selected on just one side of the die or on both sides of the die. In this case, the cavities 13 may alternatively also be provided in the corresponding die carrier component, and the piston-like projections 14 can be provided in the corresponding die half 13.

[0084] Therefore, when the lower and upper die carrier fixtures 4 a, 4 b are in engagement with one another, a preferably incompressible liquid can be fed via the fluid passages 9 to the space which remains between the piston-like projections 14 and the corresponding cavities 13, in order to apply a hydrostatic fluid chamber pressure Pa to the fluid chambers formed there.

[0085] The piston-like projections 14 of the lower die carrier fixture 4 b and the corresponding cavities 13 of the upper die carrier fixture 4 a do not necessarily have to be of cylindrical design, but rather may also adopt any desired surface-area shape. By way of example, FIG. 4a illustrates an upper die carrier fixture 15 in which an inner partial region 15″ which can be acted on by hydrostatic pressure is divided from an outer partial region 15′ via a seal 15 a of elongate, rounded surface-area form. FIGS. 4b, c and d illustrate further possible embodiments of die carrier fixtures 16, 17 and 18, partial regions 16″, 17″ and 18″ which can be acted on by hydrostatic pressure in each case being divided from outer partial regions 16′, 17′ and 18′ by seals 16 a, 17 a and 18 a, respectively, and the partial regions 16″, 17″ and 18″ which can in each case be acted on by hydrostatic pressure having an oval (FIG. 4b), hexagonal (FIG. 4c) and irregular (FIG. 4d) surface-area form.

[0086] The hydrostatic fluid chamber pressure Pa required to produce the required closure-holding force Fa is applied to the fluid chambers 8 via the respective fluid passages 9 by a preferably incompressible fluid, such as water or oil, being supplied by means of a standard hydraulic pump or the like, it being possible for the fluid chambers 8 to be acted on partially, i.e. independently of one another, or alternatively jointly by the same or a different fluid chamber pressure Pa. This allows flexible positioning of the die halves 5 a, 5 b in the die carrier 2, since the fluid chambers 8 can be actuated as a function of the position of the die halves 5 a, 5 b in the die carrier 2, so that in particular there is no need for the die 5 to be positioned centrally. Furthermore, by partial actuation of the fluid chambers 8, it is even possible to produce a uniform distribution of force for any position of the die 5 without, for example, a minimum size of die carrier 2 being required for this purpose.

[0087] To ensure that the closure-holding force Fa exerted by the die carrier components 3, 4 on the corresponding die halves 5 a, 5 b by the hydraulic application to the fluid chambers 8 is always greater than or equal to the force Fi which results from the internal high pressure Pi and is active between the die halves 5 a, 5 b throughout the entire deformation process, it is particularly advantageous for the forming chamber 6 and the fluid chambers 8 to be acted on by a uniform pressure from the same pressure source (e.g. hydraulic pump), since then the larger active surface area of the die carrier fixtures 3 b and 4 a (relative to the wall surrounding the forming chamber 6) then means that the closure-holding force Fa is always greater than the force Fi acting between the die halves 5 a, 5 b. However, it is also possible to use separate pressure sources to apply pressure to the forming chamber 6 and the fluid chambers 8.

[0088] The hydraulic pump for applying pressure to the fluid chambers 8 is preferably designed in such a way that the fluid chamber pressure Pa produced in the fluid chambers 8 located opposite one another on a force line is in each case identical. This uses a relatively low structural outlay to ensure that, given an identical application of hydrostatic pressure to the fluid chambers 8, in each case the same hydrostatic fluid chamber pressure is produced on both sides of the die 5.

[0089] However, deviations in the size of the active surface areas of the die carrier fixtures 3 b and 4 a can lead to different forces being exerted on the die 5, even though the hydrostatic fluid chamber pressure Pa applied is identical on both sides of the die 5. To compensate for deviations of this nature, it is advantageous to adjust the hydrostatic fluid chamber pressure Pa produced in the corresponding fluid chambers 8 as a function of the force Fa which is actually exerted on the die 5, a measure which can be achieved by means of a simple control circuit (not shown), which as control variable has the force Fa which is exerted on the die 5 by the corresponding die carrier component 3 or 4. By means of a control circuit of this type, it is also possible to compensate for any pressure drop in the fluid chambers 8 which may occur during the deformation process, since the fluid is tracked under control of the fluid passages 9 and the pressure in the fluid chambers 8 and/or the force Fa exerted on the die 5 is kept constant. In this case, the control circuit is preferably set in such a way that the forces exerted on the corresponding die half 5 a and 5 b by the lower die carrier fixture 3 b of the upper die carrier component 3 and by the upper die carrier fixture 4 a of the lower die carrier component 4, respectively, are oppositely directed and of the same magnitude.

[0090] The inventive way of designing the fluid chambers 8 by means of the corresponding, substantially positively-locking cavities 13 and piston-like projections 14 which are present in the respective die carrier fixtures 3 a, 3 b, 4 a and 4 b has the further effect that, in the event of a relative movement between the respective die carrier fixtures 3 a and 3 b and 4 a and 4 b, an integrated guide is formed, ensuring a substantially defined direction of movement of the die carrier fixtures 3 a, 3 b, 4 a and 4 b without further design measures being required for this purpose, which likewise contributes to maintaining the precision positive lock between the die halves 5 a, 5 b which is required for a deformation process to proceed without disruption.

[0091]FIG. 5 illustrates an alternative embodiment of a die carrier component 19 with an upper die carrier fixture 19 a and a lower die carrier fixture 19 b, in which the piston-like projections of the lower die carrier fixture 19 b and the cavities of the upper die carrier fixture 19 a are formed in such a way that, in the engaged state of the die carrier fixtures 19 a, 19 b, a continuous fluid chamber 20 is formed. The fluid chamber 20 can be uniformly acted on from the outside by a preferably incompressible hydraulic fluid via fluid passages arranged in each piston-like projection. A seal 22 is in this case provided only in the outer edge region of the die carrier component 19. The seal 22 may, for example, be arranged in an encircling channel which surrounds the entire fluid chamber 20. Consequently, the entire area between the upper and lower die carrier components 19 a, 19 b surrounded by the seal 22 is used as a hydraulically acting surface area. The interlocking piston-like projections and cavities of the die carrier components 19 a, 19 b in this case in turn effect integrated guidance of the relative movement between the two die carrier components 19 a, 19 b throughout the application of hydraulic pressure.

[0092] The principle on which the hydroforming device according to the invention and the corresponding process are based will now be explained in more detail with reference to FIGS. 6 and 7.

[0093] For this purpose, the figures illustrate an excerpt 1′ from the hydroforming device 1 from FIG. 1 without (FIG. 6) and with (FIG. 7) application of hydrostatic pressure, the elements of the hydroforming device 1 which correspond to those shown in FIG. 1 being denoted by identical reference symbols. In particular, FIGS. 6 and 7 diagrammatically depict excerpts 3′, 4′ of the die carrier components 3, 4 with corresponding excerpts 3 a′, 3 b′, 4 a′, 4 b′ from the corresponding die carrier fixtures 3 a, 3 b, 4 a, 4 b, the excerpts being selected in such a way that in each case one fluid chamber 8 with an associated fluid passage 9 is illustrated.

[0094] Once again, a die 5 with upper and lower die halves 5 a, 5 b is illustrated between the excerpts 3′, 4′ of the die carrier components 3, 4, with a fluid passage 23 which leads to the forming chamber. 6 in the manner described above also being shown.

[0095]FIG. 7 diagrammatically depicts the effects of introducing a hydrostatic internal pressure Pi into the forming chamber 6 and of a hydrostatic fluid chamber pressure Pa into the fluid chambers 9. The internal pressure Pi which is generated in the forming chamber 6 as a result of hydrostatic pressure being applied to the forming chamber 6 via the fluid passage 23 is distributed uniformly over the wall surrounding the forming chamber 6 and leads to an outwardly directed force Fi on the die halves 5 a, 5 b, as illustrated by the double arrows inside the forming chamber 6.

[0096] At the same time, the hydrostatic fluid chamber pressure Pa which is produced inside the fluid chambers 8 by application of hydrostatic pressure to the fluid passages 9 of the lower and upper die carrier components 3, 4 is distributed uniformly over the walls surrounding the fluid chambers 8, as likewise illustrated by double arrows. In this context, it should be ensured that the force Fa which corresponds to the hydrostatic fluid chamber pressure Pa is always greater than or equal to the force Fi corresponding to the hydrostatic internal pressure Pi throughout the entire deformation process, so that the precision positive lock between the die halves 5 a, 5 b which is required continues to be ensured.

[0097] As is diagrammatically depicted in FIG. 7, elastic deformations of the die carrier components 3′, 4′ occur only at those side faces of the die carrier 2′ which are remote from the die 5 (this figure illustrates the position prior to the elastic deformation by means of dashed lines) and therefore cannot be transferred to the die 5 mounted between the die carrier components 3′, 4′. Consequently, elastic deformations at the die 5 are prevented, with the result that the precision positive lock between the die halves 5 a, 5 b which is required in order to ensure that a deformation process takes place without disruption continues to be ensured.

[0098] If, in the event of an increase in the hydrostatic internal pressure Pi in the forming chamber 6, an increase in the hydrostatic fluid chamber pressure Pa should be required in order to maintain the positive lock between the die halves 5 a, 5 b, the dynamic volume compensation which takes place in the fluid chambers 8 leads to an increase in the elastic deformation on those side faces of the die carrier components 3′, 4′ which are remote from the die 5. The precision positive lock between the die halves 5 a, 5 b and therefore the pressure-tight seal throughout the entire deformation process are consequently not adversely effected by the elastic deformations of the die carrier components 3′, 4′, since such deformations are instead dissipated to the outside, for example into a frame of the hydroforming device 1′.

[0099]FIG. 8 diagrammatically depicts an excerpt from a hydroforming device according to the invention in which a die 5′ in accordance with a further preferred embodiment is provided. The other components, corresponding to the hydroforming device from FIG. 6, are denoted by identical reference symbols.

[0100] In accordance with FIG. 8, the die 5′ is designed in such a way that a forming element 5′c is provided in the die parting plane between the two die halves 5′a, 5′b of the die 5′. The forming element 5′c may, for example, have the surface geometry shown in FIG. 8 or alternatively any other desired surface geometry, depending on the desired surface geometry of the workpiece which is in each case to be deformed. The forming element 5′c in each case forms a forming chamber 6 a and 6 b, which can be acted on by a hydrostatic internal pressure Pi for shaping purposes at in each case one workpiece which is to be deformed (not shown), with each of the die halves 5′a, 5′b.

[0101] In order to achieve pressure-tight mounting of the forming element 5′c between the die halves 5′a, 5′b, the die halves 5′a, 5′b, in accordance with the embodiment illustrated in FIG. 8, preferably each have end-side shoulders facing the forming element 5′c, seals (not shown) in each case being provided between these shoulders and the adjoining end sections of the forming element 5′c. In this case, the surrounding wall of each forming chamber 6 a, 6 b is formed by the end-side shoulders provided at the die halves 5′a, 5′b and the mutually facing side faces of the corresponding die half 5′a, 5′b and the forming element 5′c.

[0102] In accordance with FIG. 8, both forming chambers 6 a, 6 b can be acted on, in a similar manner to the embodiment illustrated in FIG. 6, with a hydraulic internal pressure Pi via fluid passages 23 a, 23 b, which are connected, for example, to a hydraulic pump (not shown).

[0103] When the embodiment illustrated in FIG. 8 is operating, the opened hydroforming device is in each case fitted with a workpiece which is to be deformed (not shown) between the forming element 5′c and the associated die half 5′a or 5′b, whereupon the two die halves 5′a, 5′b are brought into contact with the forming element 5′c at its end sections, leading to the formation of the forming chambers 6 a, 6 b. Then, the deformation process is carried out by application of hydraulic pressure to the forming chambers 6 a, 6 b via the fluid passages 23 a, 23 b, in a similar manner to the embodiment presented in conjunction with FIGS. 6 and 7. As has already been described above, during this deformation process a hydrostatic external pressure Pa which compensates for the hydrostatic internal pressure Pi in the forming chambers 6 a, 6 b is produced in the fluid chambers 8 by application of hydraulic pressure to the fluid chambers 8, so that the required die-closing force of the hydroforming device is ensured.

[0104] When the die is fitted with workpieces which are to be deformed, each of the forming chambers 6 a and 6 b is divided into a pressure chamber and a deformation chamber by the corresponding workpiece. While the hydrostatic internal pressure Pi is applied to the pressure chamber facing the corresponding fluid passage 23 a, 23 b, deformation takes place in the deformation chamber located on the opposite side of the workpiece.

[0105] Moreover, the forming element 5′c preferably has outlet openings (not shown), as will be explained in more detail in connection with FIGS. 11a-c.

[0106] The forming element 5′c itself is preferably secured to the frame, which also bears the die carrier 2.

[0107] To ensure that identical hydrostatic pressure ratios can be produced in a simple way in the forming chambers 6 a and 6 b on both sides of the forming element 5′c by the application of hydraulic pressure, the forming element 5′c is of mirror-symmetrical construction with regard to the die parting plane, so that forming chambers 6 a, 6 b of corresponding geometry can be formed. In this case, it is possible for both forming chambers 6 a, 6 b to be acted on by an identical hydrostatic internal pressure Pi in a simple way, so that two corresponding components are formed in a single production step.

[0108] As can be seen from FIG. 9, with the hydroforming device according to the invention it is also possible for the fluid chambers of a plurality of die carrier components to be connected next to one another in an assembly, so that devices with considerable overall sizes of a length of many metres and high closure-holding forces are obtained.

[0109]FIG. 9 illustrates the die carrier 2 from FIG. 1 assembled with a further die carrier 24 of identical design and with die carrier components 25, 26, each of the die carriers 2, 24 being mounted in a frame 27 and 28, respectively. In this case, the lower die carrier components 4 and 26 of the die carriers 2, 24, respectively, are preferably in each case integrated in a clamping table (press platen).

[0110] Each of the frames 27 and 28 is composed of horizontal connecting bars 31 and 32 secured to vertical lamellae 29 and 30, respectively, it being possible for the lamellae 29, 30 and the connecting bars 31, 32 to be made, for example, from steel. The die carrier components 3 and 4 and 25 and 26 of the die carriers 2 and 24, respectively, are once again guided on the vertical lamellae 29 and 30 in such a manner that they can move in the vertical direction via guides (not shown) and can be locked in any desired position and are otherwise constructed in accordance with the die carrier components 3 and 4 of the embodiment illustrated in FIGS. 1 to 3.

[0111] The two frames 27 and 28 are positioned adjacent to one another, in such a way that the die carrier components 3 and 25 and 4 and 26 received therein are in each case arranged adjacent to one another. The two die carriers 2 and 24 form a functional unit to the extent that they form a continuous die carrier with a correspondingly enlarged horizontal cross-sectional area. The result is a hydroforming device assembly comprising individual hydroforming devices which form a functional unit.

[0112] Once again, a die 33 which is divided into die halves 33 a, 33 b is accommodated in the hydroforming device assembly comprising the two die carriers 2 and 24 formed in this way, the die halves 33 a, 33 b forming a forming chamber 34 which can be acted on by the hydrostatic internal pressure Pi via a fluid line 36 which leads to a diagrammatically indicated hydraulic pump 35. In the exemplary embodiment illustrated, the hydraulic pump 35 is likewise used to apply the hydrostatic fluid chamber pressure Pa to the fluid chambers 8. In the case of the assembly of die carriers 2, 24 illustrated in FIG. 9, the die 33, like the forming chamber 34 formed therein, can have an enlarged cross-sectional area parallel to the horizontal connecting bars 31, 32 relative to the individual die carrier 2, so that it is now also possible to process correspondingly larger sheet-metal goemetries.

[0113]FIGS. 10a-10 d illustrate various designs of die arrangements 40-70 in accordance with the invention in which a relatively large number of workpieces can be deformed in a single production step, so that the economics of the corresponding hydroforming device are significantly improved.

[0114] In accordance with FIG. 10a, in a die arrangement 40 a plurality of die components 41, 42, 45 and 46 are arranged in a stacked arrangement in a direction which is perpendicular to the die parting planes, in which arrangement in each case two adjacent die components, such as for example the die components 41 and 45 or 45 and 46, can be considered die halves of one of a plurality of dies of the die arrangement 40.

[0115] The die halves 41, 42, 45 and 46 are in this case designed in such a way that die components 41, 42, which in a similar manner to the embodiment illustrated in FIG. 6 and FIG. 7 each have a fluid passage 43 and a seal 44 (which is only diagrammatically depicted), are in each case arranged at the upper and lower ends of the stacked arrangement 40. Between the die components 41, 42, die components 45 which have a shaping action on both sides and die components 46 which are provided with a supply of fluid on both sides are arranged in an alternating sequence between the die components 41, 42, each pair of adjacent die components 45, 46 in each case forming a die. The die components 46 which are provided with a fluid supply on both sides in each case have a fluid passage 47 which branches in a “T shape” in the direction towards the adjacent die components 45, and also a diagrammatically depicted seal 48.

[0116] The seals 44 and 48 can be of any desired configuration, provided that it is ensured that, when the die arrangement 40 is closed, the pressure chambers “A” are sealed off in a fluid-tight manner. Alternatively, however, it is also possible to dispense with the seals 44 and 48, in which case, when the die arrangement 40 is operating, any fluid which escapes from the pressure chambers “A” is topped up via the fluid passages 43 and 47.

[0117] In accordance with FIG. 10a, the dies formed from the die components or die halves 45, 46 are each equipped with a workpiece 49 which is to be deformed and is arranged in the associated die parting plane, the workpieces 49 which are to be deformed being in the form of planar metal sheets in accordance with FIG. 10a.

[0118] When workpieces 49 which are to be deformed are being mounted in the die arrangement 40, with the die arrangement 40 closed, a pressure chamber “A”, which can be acted on by a hydrostatic internal pressure (Pi) for shaping purposes at the workpiece 49 is in each case formed by each workpiece 49 and one die half, e.g. the top die component 21, and a deformation chamber “B” is formed by the workpiece 49 and the other die half, in this example the die component 45, between in each case two adjacent die halves 41 and 45, 45 and 46 or 45 and 42. Therefore, in the embodiment illustrated in FIG. 10a, the sequence of pressure chambers “A” and deformation chambers “B” can be schematically described as “ . . . A-B-B-A . . . ”. The “T-shaped” branching of the fluid passages 47 ensures that the respectively adjacent pressure chambers “A” are acted on by an identical hydrostatic internal pressure Pi.

[0119] With the die arrangement 40 closed, each deformation chamber “B” is in fluid communication with the external surroundings of the die arrangement 40 via outlet openings (not shown) in the respectively adjacent die half. These outlet openings have the effect that when pressure is applied to the pressure chamber “A”, a build-up of pressure in the adjacent deformation chamber “B” is prevented. This facilitates the deformation of the workpiece 49, since the movement of the workpiece 49 towards the deformation chamber “B” which takes place during the deformation does not lead to a build-up of a counter pressure despite the associated reduction in volume of the deformation chamber “B”.

[0120] The embodiment of a die arrangement 50 which is illustrated in FIG. 10b, like the die arrangement 40 from FIG. 10a, is such that in each case a die half which in each case forms a deformation chamber “B” together the adjacent workpieces 49 and 59 and a die half which in each case forms a pressure chamber “A” with the adjacent workpieces 49 and 59 are arranged adjacent to one another in an alternating sequence perpendicular to the die parting plane. Moreover, the die arrangement 50 has the same sequence of pressure chambers “A” and deformation chambers “B”, namely “ . . . A-B-B-A . . . ”. The embodiment of a die arrangement 50 which is illustrated in FIG. 10b therefore substantially corresponds to the die arrangement 40 shown in FIG. 11a, and consequently to this extent the corresponding components are provided with corresponding reference symbols.

[0121] Unlike in the case of the die arrangement 40, in the die arrangement 50 the fluid-supplying die components 56 each have two separate fluid passages 57 a, 57 b which branch off towards opposite directions of the fluid-supplying die component 56, namely in each case towards the adjacent workpieces 59. Therefore, the respectively adjacent pressure chambers “A” can be acted on by different hydrostatic pressures via the fluid passages 57 a, 57 b.

[0122] Of course, the die components or die halves 45 and 55 are not necessarily of single-piece design, but rather may also be of multi-piece design, in particular may for example be divided along the die parting plane into two or more die component elements. A division into separate die component elements of this type has the advantage that the abovementioned outlet openings (not shown) in the die components 45 and 55 for preventing a build-up of pressure in the deformation chambers “B” can be produced more easily in manufacturing technology terms, since for this purpose, by way of example, outlet passages which are to be provided perpendicular to the die parting plane only have to be of correspondingly reduced length.

[0123] Accordingly, it is also possible for the two die halves which are located between two forming elements and are in each case assigned to the adjacent forming elements to be designed as separate components or as a single piece.

[0124] Exemplary embodiments of die components 100, 200 and 300 are illustrated in FIGS. 11a-c.

[0125] In accordance with FIG. 11a, these outlet openings may, for example, comprise an outlet passage 101 extending parallel to the die parting plane and a plurality of outlet passages 102 arranged perpendicular thereto. By means of outlet passages 101, 102 of this type, it is possible to ensure that, when the die component 100 which has been fitted in a hydroforming device according to the invention is provided with a workpiece, a build-up of pressure in the region between the workpiece and the adjoining die half is prevented if the pressure chamber formed on the opposite side of the workpiece is acted on by the hydrostatic internal pressure. Depending on the specific requirements, in particular depending on the geometry and/or dimensions of the workpieces which are to be deformed, the outlet passages 101, 102 may have different dimensions and/or geometries; by way of example, outlet passages 101, 102 in the form of cylindrical bores with a diameter in the range from 0.1 mm to 1 mm may be suitable.

[0126] Furthermore, FIG. 11b illustrates an embodiment of a die component 200 which only has a shaping action on one side, i.e. has a shaping pattern for deformation of a workpiece in the hydroforming device on only one side. Accordingly, an outlet passage 201 extending parallel to the die parting plane is provided, from which outlet passage 201 a plurality of outlet passages 202, arranged perpendicular thereto, extend towards the shaping side. To form a fluid-supplying side, a fluid passage 203 extends towards the opposite side of the die component 200 from this shaping side, a seal 204 also being provided, in a similar manner to in the embodiment described above.

[0127]FIG. 11c shows an embodiment of a die component 300 which is divided in two along the die parting plane, i.e. is of two-piece design. Otherwise, the die component 300 is designed to have a shaping action on both sides, in a similar manner to the die component 101 shown in FIG. 11a, i.e. it has in particular outlet passages 301, 302 which extend toward the two opposite shaping sides. The two-piece embodiment of the die component 300 is advantageous in particular from a manufacturing technology perspective, since the outlet passages 301, 302 running perpendicular to the die parting plane have a length which is shorter, in particular only half as great, as the corresponding outlet passages 102 of the die component 100 have to be.

[0128] In accordance with the die arrangement 60 shown in FIG. 10c, an upper die component 61 which has a shaping action on one side towards the lower die component 62 and a lower die component 62 are provided, the lower die component 62 having a seal 63 and a fluid passage 64 in the direction of the upper die component 61. A plurality of, in the exemplary embodiment a total of five, identical die components 65 are arranged in a stacked form, in a direction perpendicular to the die parting plane, between the die components 61, 62. Each of the die components 65 has a fluid passage 66 extending towards the upper die component and a seal 67 which is likewise arranged in this direction. The die arrangement 60 is likewise fitted with workpieces 68 arranged in the corresponding die parting planes, so that in each case a pressure chamber “A” and a deformation chamber “B” are formed in an alternating sequence perpendicular to the die parting plane between the workpieces 68 and the die components 61 and 65, 65 and 65 and 65 and 62. Therefore, in the die arrangement 60 illustrated in FIG. 10c, the sequence of pressure chambers “A” and deformation chambers “B” can be schematically presented as “ . . . A-B-A-B . . . ”.

[0129] As can be seen from the embodiment of a die arrangement 70 illustrated in FIG. 10d, it is also possible for combinations of die components to be arranged in a stacked arrangement in a direction perpendicular to the die parting plane. The die arrangement 70 has an upper die component 71 and a lower die component 72.

[0130] The die components 71, 72 each have a fluid passage 73 and 75, respectively, and a seal 74 and 76, respectively, in a mutually facing direction. Starting from the upper die component 71, the following parts are arranged between the die components 71, 72, in succession in a stacking direction perpendicular to the die parting plane:

[0131] a die component 77 which has a shaping action on both sides,

[0132] a die component 78 which has a fluid passage 79 extending towards this die component 77 and a seal 80 which likewise faces in this direction, and which is designed to have a shaping action on one side, specifically the side facing away from this direction,

[0133] a die component 81 with a fluid passage 82 which branches in a T-shape and a seal 83 on both sides,

[0134] a further die component 77 which has a shaping action on both sides, a further die component 78 with fluid passage 79 and seal 80 which has a shaping action on one side,

[0135] a further die component 84 with fluid passages 84 a, 84 b which are formed separately from one another and extend on both sides, and a seal 85 on both sides, and

[0136] a further die component 77 which has a shaping action on both sides.

[0137] The stacked arrangement is in this case selected in such a way that, when the die arrangement 70 is fitted with workpieces 86, once again a pressure chamber “A” and a deformation chamber “B” are formed on opposite sides of the workpiece. Provided that this sequence is ensured, the stacked sequence of pressure chambers “A” and deformation chambers “B” in the die arrangement 70 can otherwise be described as irregular, specifically, in the exemplary embodiment illustrated, as “A-B-B-A-B-A-A-B-B-A-B-A-A-B-B-A”.

[0138] In all the die arrangements 40-70 which have been illustrated, it is possible for the die components which have a shaping action on one side and/or the die components which have a shaping action on both sides, on the side which is in each case used for shaping purposes, to have any desired shaping structure on the surface in question.

[0139] The individual forming chambers and/or the fluid passages connected thereto can be acted on by the required hydrostatic internal pressure from various pressure sources or from a single pressure source (e.g. a hydraulic pump). Furthermore, these forming chambers as well as the fluid chambers 8 which are provided for the purpose of producing the required closure-holding force Fa in the die carrier 2 can be acted on by a uniform pressure from the same pressure source, which in turn ensures that, on account of the larger active surface areas of the die carrier fixtures 3 b, 3 b′ and 4 a, 4 a′, the closure-holding force Fa is always greater than the force Fi which is active inside the forming chambers. However, it is also possible to use separate pressure sources to apply the pressure to the forming chambers and the fluid chambers 8.

[0140] List of Reference Symbols

[0141]1 Hydroforming device

[0142]2 Die carrier

[0143]3 Die carrier component

[0144]4 Die carrier component

[0145]3 a, 4 a Die carrier fixture

[0146]3 b, 4 b Die carrier fixture

[0147]5, 5′ Die

[0148]5 a, 5′a Die half

[0149]5 b, 5′b Die half

[0150]5′c Forming element

[0151]6, 6 a, 6 b Forming chamber

[0152]7 Workpiece

[0153]8 Fluid chamber

[0154]9 Fluid passage

[0155]10 Seal

[0156]11 Groove

[0157]12 Sealing ring

[0158]13 Cavities

[0159]14 Piston-like projection

[0160]15 Die carrier fixture

[0161]16 Die carrier fixture

[0162]17 Die carrier fixture

[0163]18 Die carrier fixture

[0164]15′, 18′ Partial region which can be acted on by hydraulic means

[0165]15″-18″ Outer partial region

[0166]15 a-18 a Seals

[0167]19 Die carrier fixture

[0168]20 Fluid chamber

[0169]21 Fluid passage

[0170]22 Seal

[0171]23, 23 a, 23 b Fluid passage

[0172]24 Die carrier

[0173]25 Die carrier component

[0174]26 Die carrier component

[0175]27 Frame

[0176]28 Frame

[0177]29 Vertical lamellae

[0178]30 Vertical lamellae

[0179]31 Horizontal connecting bars

[0180]32 Horizontal connecting bars

[0181]33 Die

[0182]33 a, 33 b Die halves

[0183]34 Forming chamber

[0184]35 Hydraulic pump

[0185]36 Fluid line

[0186]40 Die arrangement

[0187]41 Die component

[0188]42 Die component

[0189]43 Fluid passage

[0190]44 Seal

[0191]45 Die component

[0192]46 Die component

[0193]47 Fluid passage

[0194]48 Seal

[0195]49 Workpiece

[0196] “A” Pressure chamber

[0197] “B” Deformation chamber

[0198]50 Die arrangement

[0199]51 Die component

[0200]52 Die component

[0201]53 Fluid passage

[0202]54 Fluid passage

[0203]55 Die component

[0204]56 Die component

[0205]57 a, 57 b Fluid passages

[0206]58 Seal

[0207]59 Workpiece

[0208]60 Die arrangement

[0209]61 Die component

[0210]62 Die component

[0211]63 Seal

[0212]64 Fluid passage

[0213]65 Die component

[0214]66 Fluid passage

[0215]67 Seal

[0216]68 Workpiece

[0217]70 Die arrangement

[0218]71 Die component

[0219]72 Die component

[0220]73 Fluid passage

[0221]74 Seal

[0222]75 Fluid passage

[0223]76 Seal

[0224]77 Die component

[0225]78 Die component

[0226]79 Fluid passage

[0227]80 Seal

[0228]81 Die component

[0229]82 Fluid passage

[0230]83 Seal

[0231]84 Die component

[0232]85 Seal

[0233]86 Workpiece

[0234]100 Die component

[0235]101 Outlet passage

[0236]102 Outlet passage

[0237]200 Die component

[0238]201 Outlet passage

[0239]202 Outlet passage

[0240]203 Fluid passage

[0241]204 Seal

[0242]300 Die component

[0243]301 Outlet passage

[0244]302 Outlet passage 

1. Hydroforming device, comprising at least one die (5, 5′) which is divided into two die halves (5 a, 5 b) along a die parting plane, the two die halves (5 a, 5 b) forming at least one forming chamber (6) which can be acted on by a hydrostatic internal pressure (Pi) for forming purposes at a workpiece (7) which is to be deformed, a die carrier (2), which for each die half (5 a, 5 b) has at least one die carrier component (3, 4) assigned to this die half (5 a, 5 b), each pair made up of die carrier component (3, 4) and die half (5 a, 5 b) being assigned at least one fluid chamber (8) which is formed from a piston component and a piston-receiving component, and means being provided for producing a hydrostatic fluid chamber pressure (Pa), which is at least equal to the hydrostatic internal pressure (Pi), in each of the fluid chambers (8), which fluid chamber pressure, compensating for the hydrostatic internal pressure (Pi), exerts a die-closing force on the two die halves (5 a, 5 b) wherein in each case a plurality of adjacent fluid chambers (8) are provided on opposite sides of the die (5), and wherein the means for producing the hydrostatic fluid chamber pressure (Pa) are configured in such a way that the fluid chambers (8), partially and/or jointly, can be acted on by an identical or different fluid chamber pressure (Pa).
 2. Device according to claim 1, in which at least one pair comprising piston component and associated piston-receiving component is formed by a die carrier component (3, 4) and the associated die half (5 a, 5 b).
 3. Device according to claim 1, in which at least one pair comprising piston component and associated piston-receiving component is formed by two die carrier fixtures (3 a, 3 b, 4 a, 4 b) of the corresponding die carrier component (3, 4).
 4. Device according to claim 3, in which, in the case of at least one die carrier component (3, 4), one associated die carrier fixture (3 a, 4 b) is provided with piston-like projections (14) in order to form the piston component, and the other die carrier fixture (3 b, 4 a) is provided with corresponding cavities (13).
 5. Device according to claim 4, in which each pair of cavities (13) or piston-like projections (14) in each case encloses a fluid chamber (8).
 6. Device according to anyone of the preceding claims, in which there are means for guiding the die carrier components (3, 4).
 7. Device according to anyone of the preceding claims, in which fluid chambers (8) which are respectively assigned to two different die halves (5 a, 5 b) are arranged opposite one another.
 8. Device according to anyone of the preceding claims, in which each pair comprising piston component and associated piston-receiving component in each case forms a sealing unit which seals off each fluid chamber (8) in a pressure-tight manner.
 9. Device according to anyone of claims 1 to 8, in which the fluid chambers (8), perpendicular to the piston axis, are each round or oval in cross section.
 10. Device according to anyone of claims 1 to 8, in which the fluid chambers (8), perpendicular to the piston axis, are each triangular or rectangular in cross section.
 11. Device according to anyone of the preceding claims, in which the means for producing the hydrostatic fluid chamber pressure (Pa) are configured in such a way that the fluid chamber pressure (Pa) which is produced in the fluid chambers (8) located opposite one another is in each case identical.
 12. Device according to anyone of the preceding claims, in which the means for producing the fluid chamber pressure (Pa) are configured in such a way that the forces exerted on the two die halves (5 a, 5 b) by the fluid chamber pressure (Pa) are oppositely directed and are of equal magnitude.
 13. Device according to anyone of the preceding claims, in which there is a control circuit for controlling the hydrostatic fluid chamber pressure (Pa) as a function of the force exerted on the corresponding die half (5 a, 5 b).
 14. Device according to anyone of the preceding claims, in which the die carrier (2) is integrated in a clamping table for clamping the die halves (5 a, 5 b) in place.
 15. Device according to anyone of the preceding claims, in which between the two die halves (5′a, 5′b) of the die (5′), in the die parting plane, there is a forming element (5′c), which together with each of the die halves (5′a, 5′b), in each case forms a forming chamber (6 a, 6 b) which can be acted on by a hydrostatic internal pressure for shaping purposes at in each case one workpiece which is to be deformed.
 16. Device according to claim 15, in which the forming element (5′c) is of mirror-symmetrical construction with regard to the die parting plane.
 17. Device according to claim 15 or 16, in which the forming element (5′c) between the die halves (5′a, 5′b) is secured to a frame which bears the die carrier (2).
 18. Device according to claim 15 or 16, in which the forming element (5′c) is surrounded in a pressure-tight manner by the die halves (5′a, 5′b).
 19. Device according to claim 18, in which the forming element (5′c) is mounted in a floating position between the two die halves (5′a, 5′b).
 20. Device according to anyone of claims 15 to 19, in which a plurality of dies (5) are arranged adjacent to one another in a direction which is perpendicular to the die parting plane.
 21. Device according to claim 20, in which in the die parting plane of at least one of the dies (5), there is a forming element (5′c) provided between the respective die halves (5′a, 5′b), which forming element, together with each of the associated die halves (5′a, 5′b), in each case forms a forming chamber (6 a, 6 b) which can be acted on by a hydrostatic internal pressure for shaping purposes at in each case one workpiece which is to be deformed.
 22. Hydroforming device assembly, comprising at least two devices according to anyone of claims 1 to 21, which form a functional unit.
 23. Hydroforming die arrangement (40-70), in which a plurality of dies, which are in each case divided into two die halves along a die parting plane, are arranged in a stacked arrangement in a direction which is perpendicular to the die parting planes, in which arrangement, during mounting of the die arrangement (40, 50, 60, 70) between in each case two adjacent die halves (41-71, 45-75, 46-76, 42-72) together with a workpiece which is to be deformed, a pressure chamber (A), which can be acted on by a hydrostatic internal pressure (Pi) for shaping purposes at the workpiece, is formed by the workpiece and one die half, and a deformation chamber (B) is formed by the workpiece and the other die half; and the deformation chamber (B) being in fluid communication, via the respectively adjacent die half, with the surroundings of the die arrangement (40-80), so that when pressure is applied to the pressure chamber (A), pressure is prevented from building up in the deformation chamber (B).
 24. Hydroforming die arrangement according to claim 23, in which the die half which adjoins the corresponding deformation chamber. (B) has outlet openings (101, 102, 201, 202, 301, 302) extending from the surroundings of the die to the corresponding deformation chamber (B).
 25. Hydroforming die arrangement according to claim 24, in which the outlet openings (101, 102, 201, 202, 301, 302) comprise at least one outlet passage (101, 201) extending parallel to the die parting plane and a plurality of outlet passages (102, 202) arranged perpendicular thereto.
 26. Hydroforming die arrangement according to claim 23 or 24, in which the die half (300) which adjoins the corresponding deformation chamber (B) is divided along the die parting plane at least into two separate components (300 a, 300 b), which each have outlet openings (301, 302) extending perpendicular to the die parting plane toward the corresponding deformation chamber (B).
 27. Hydroforming die arrangement according to anyone of claims 23 to 26, in which the stacked arrangement is such that in each case one die half which in each case forms a deformation chamber (B) with the adjacent workpieces (49-89) and one die half which in each case forms a pressure chamber (A) with the adjacent workpieces (49-89) are arranged adjacently, in an alternating sequence, perpendicular to the die parting plane (FIGS. 10a, 10 b).
 28. Hydroforming die arrangement according to claim 27, in which at least one of the die halves which in each case forms a pressure chamber (A) with the adjacent workpieces (49-89) has a fluid passage, which branches off towards the two workpieces (49-89), for applying the hydrostatic internal pressure (Pi) to the pressure chambers (A) (FIG. 10a).
 29. Hydroforming die arrangement according to claim 27 or 28, in which at least one of the die halves-which in each case forms a pressure chamber (A) with the adjacent workpieces (49-89) has two fluid passages which branch off in opposite directions for independent application of the hydrostatic internal pressure (Pi) to the corresponding pressure chambers (A) (FIG. 10b).
 30. Hydroforming die arrangement according to anyone of claims 23 to 26, in which the stacked arrangement is such that in each case one pressure chamber (A) and one deformation chamber (B) are formed in an alternating sequence perpendicular to the die parting plane (FIG. 10c).
 31. Hydroforming process, in which in at least one die (5), which is divided into two die halves (5 a, 5 b) along a die parting plane, at least one forming chamber (6), which is formed by the die halves (5 a, 5 b), is acted on by a hydrostatic internal pressure (Pi) for shaping purposes at a workpiece (7) which is to be deformed, and in which a hydrostatic fluid chamber pressure (Pa), which is in each case at least equal to the internal pressure (Pi) and, compensating for the hydrostatic internal pressure (Pi), exerts a die-closing force on the two die halves (5 a, 5 b), is produced in fluid chambers (8) which are formed from a piston component and a piston-receiving component and are each assigned to one of the die halves (5 a, 5 b) wherein in each case a plurality of adjacent fluid chambers (8) on opposite sides of the die (5) are partially and/or jointly acted on by an identical or different fluid chamber pressure (Pa).
 32. Process according to claim 31, in which the hydrostatic fluid chamber pressure (Pa) is controlled as a function of the force which is exerted on the corresponding die half (5 a, 5 b) by the fluid chamber (8).
 33. Process according to claim 31 or 32, in which, in the die (5′), two forming chambers (6′a, 6′b), which are arranged opposite one another and are each formed by in each case one of the die halves (5′a, 5′b) with a forming element (5′c) arranged in the die parting plane between the two die halves (5′a, 5′b) of the die (5′), are simultaneously acted on by a hydrostatic internal pressure.
 34. Process according to claim 33, in which the forming element (S′c) is arranged mirror-symmetric-ally with respect to the die parting plane, and the two forming chambers (6 a, 6 b), in order to form two identical components from workpieces which are in each to be deformed, are simultaneously acted on by an identical hydrostatic internal pressure (Pi).
 35. Process according to claim 33 or 34, in which, in a plurality of dies (5) which are arranged adjacent to one another perpendicular to the respective die parting plane and have forming elements (5′c) provided in the respective die parting plane between the respective die halves (5′a, 5′b), a plurality of forming chambers, which are in each case formed by in each case one of the die halves (5′a, 5′b) and one of the forming elements (5′c), are simultaneously acted on by a hydrostatic internal pressure.
 36. Hydroforming process, in which, in a hydroforming die arrangement (40-70) in which a plurality of dies which are in each case divided into two die halves along a die parting plane are arranged in a stacked arrangement in a direction perpendicular to the die parting planes, the die arrangement (40, 50, 60, 70) is equipped, between in each case two adjacent die halves (41-71, 45-75, 46-76, 42-72), with a workpiece which is to be deformed, so that a pressure chamber (A) is formed by the workpiece and one die half and a deformation chamber (B) is formed by the workpiece and other die half; each of the pressure chambers is acted on by a hydrostatic internal pressure (Pi) for shaping purposes at the corresponding workpiece; and when pressure is applied to the pressure chamber (A), a build-up of pressure in the deformation chamber (B) is prevented by means of at least one fluid connection between the respectively adjacent die half and the surroundings of the die arrangement (40-80). 